The goal of a majority of orthopedic surgery is restoring the function of joints in the human skeletal system. A variety of artificial joints and parts of joints, known as prostheses and implants, are used to reconstruct joints with proper positioning and alignment. The best outcomes of operations involving such prostheses rely on optimal selection and alignment of the prostheses in accordance with the original anatomy. Each joint may vary in contour and size in different body sizes. Deformities like fractures are also different in size and shape. Further, bone quality also changes by age. As a result, currently each commercially available prosthesis for a given joint is offered in a variety of shapes and sizes by different manufactures to accommodate each individual indication.
Although a variety of prostheses is available for different patient needs, this same variety has made it more difficult for clinicians to select the most appropriate size and manufacturer for a given clinical situation. Difference between sizes and shapes of each particular implant is not easily discernable. One of the key problems in optimization of orthopedic surgery is selecting the right size of implant that allows for proper fit and alignment.
An undersized prosthesis can result in poor fixation and early loosening, while an oversized prosthesis can lead to intra-operative fracture. For example, in total hip arthroplasty, a tight press-fit interface is desirable when placing the femoral prosthesis. A stem that is too small will not be stable and eventually subside inside the femoral canal. Attempting to insert an oversize stem will result intraoperative fracture and complication. It is well known in the clinical community that these issues are sometimes not identified until after the surgery is completed, resulting in devastating post-operative complication. Such complications have been reported in up to 24% of patients.
Templating
To help reduce these problems, pre-operative planning has been conventionally performed to select suitable implants from the variety of different sizes and shapes available. Templating is an important part of pre-operative planning for an orthopedic arthroplastic operation to select an implant suited by its size and shape for use in replacement of a particular joint in a particular patient.
An acetate template is a magnified outline drawing of a particular prosthesis in one size and shape, printed on a transparent overlay. Acetate templates are typically provided by prosthesis manufacturers. They come in a set of different sizes, for example, up to twenty for some implants. These transparencies are placed on pre-operative radiographs, usually plain x-rays, over the bony structure which is going to be replaced during the operation, in the desired orientation to identify the most appropriate prosthesis, size and shape, as well as the proper place and orientation to restore alignment and create maximum stability for reconstructed joint.
Templating before operation provides the surgeon the opportunity to: anticipate specific problems; determine the most appropriate type, size and shape of available prosthesis; prevent possible intra-operative and post-operative complications; optimize biomechanics by restoring proper alignment; and ensure availability of the desired prosthesis.
Benefits of templating include improvement of surgical accuracy, restoration of biomechanics of joints and limbs, decreased complications such as fractures and subsidence, reduced operative time, and more long-lasting outcome.
Conventional templating also has some fundamental drawbacks. It does not address and reconcile the fact that the magnification of pre-operative radiographs varies by patients' body size, while implant manufacturers supply only one set of acetate templates with a single magnification factor (usually 120%) for each particular prosthesis. This discrepancy therefore can lead to unreliable measurement and sizing information. Pre-operative planning is only possible when both x-ray and sets of acetate templates are available. Printing and storing radiographic films is costly for hospitals and centers. Acetate templates are subject to physical wear and tear, and they can be misplaced, such that will not be available at the time needed for templating. A few sets of up to twenty templates for each type of implant may be required for optimal pre-operative planning Total number of required sets of templates multiplies by the number of operating rooms in a hospital, as they need to be available in each operating room. Production, distribution and storage of acetate templates are expensive and impose large burdens on manufacturers and hospitals alike.
Recent Advances in Radiographic Imaging Technology
Hospitals have been replacing their old technology radiology systems with digital systems across the United States. Nowadays, digital image acquisition, processing, and viewing with computers are used instead of the old standard techniques of obtaining radiographs and conventional film screening. They have been exchanging their old film storages for picture archiving and communications systems (PACS). This digital system saves time, expense, and resources required for acquiring, storing, and retrieving the images and information that were once saved on film. It also has reduced the costs associated with a superfluous inventory of prostheses. A hospital does not have to have all different sizes of all different implants in inventory at all the time, only the sizes that are going to be used in next few days. If cases are templated in advance, implants and sizes will be known.
Like other digital images, a major advantage of digital radiographic images is their accessibility, which is practically from anywhere and immediately. The only requirement is a computer with connection to a network or the internet. These images can easily be stored and transferred by digital media or via network and internet, and they can be duplicated to unlimited numbers without losing quality.
Digital Templating
One major advantage of recent advances in radiographic imaging technology is using software for viewing digital radiographic images. It has had a substantial impact on orthopedic surgery by making it possible to perform pre-operative planning, including digital templating, electronically on a computer using special software.
A limited variety of digital templating software has been developed during past few years. They provide a library of digital versions of the templates of different kinds of prostheses, in different sizes and shapes, that a user can place on a radiographic image and use for pre-operative planning They also provide many different tools for making different kinds of evaluations and measurements; such as angles, length, distance, etc.
Such templating software offers improved precision in measurements as it can measure fractions of millimeters and degrees, while traditional visual measurement, even in the best situation, can only get close to one millimeter.
Published studies have shown the following advantages for digital templating: It is more accurate than conventional method when done properly. It is quicker and more efficient than the conventional technique. It eliminates magnification error by accurately rescaling the radiographic image. It permits better choice of prosthesis size and shape. It is cost-efficient by eliminating the need for printed radiographs and required labor and storage. It eliminates need for numerous copies of the acetate templates of the available implants or when a new prosthesis becomes available. By eliminating the need for acetate templates, manufacturers save the cost required for their production and distribution. The data is easily accessible and the templated image can be transferred electronically to the operating rooms and be used during operation. Permanent electronic records can be generated and stored for further use. It is environmentally safe while acetate templates are dangerous for environment
Introduction of digital templating software has allowed orthopedic surgeons to overcome shortfalls of conventional templating in a cost-effective way.
As mentioned above, many hospitals have converted to PACS for radiographic image acquisition and storage. For those that also have digital templating software, they save on the cost of printing films for pre-operative planning, and they do not have to spend precious economic resources on space and labor necessary to store and retrieve film.
Currently Available Options for Digital Templating
Currently available templating software can be categorized into three major groups.
1. Integrated applications.
Templating software is integrated into the PACS as an option available for additional cost. This group requires additional interface application software to communicate with PACS via network to import the radiographic image for further evaluation and templating. This type of software is typically brand-specific and works only with same brand of PACS.
2. Non-PACS applications.
The templating software is independent from PACS but still requires additional interface application software and network connection with the PACS server to communicate and import images for templating purposes. Compatibility of this group with different PACS is always an issue and needs constant upgrading as new systems are developed and periodically introduced to market. This is a major contributing factor in their high maintenance cost, which is ultimately transferred to end users and payors.
3. Web-based applications.
Web-based templating software, like the non-PACS group, is independent from PACS, but unlike the non-PACS group, it requires internet connection. The user has to connect to a web-based digital software provider's website via internet access and log in to a user account. The user then has to create a new case for each patient and upload the previously saved images to the website in order to use their templating software for pre-operative planning. In another embodiment, special PACS-specific software (for additional cost) is used to upload images directly from the PACS. The templated x-ray then has to be downloaded.
The conventional technique of pre-operative templating has become increasingly impractical with the implementation of digital image acquisition technology and digital image viewing. Notwithstanding the variety of available options and having PACS as their radiology system, many hospitals still have not taken advantage of digital templating, and it is not widely used. Up to now, major barriers to widespread use of digital templating software have been the high initial purchase cost as well as the need to maintain all available digital templating software products. The only currently available web-based option also requires costly subscription.